Plague
by BobH2
Summary: Now a spy in the heart of the Federation, the Jim Kirk of the mirror universe is on the Enterprise when the testing of a new secret weapon unleashes a horror that could bring down both the Federation and the Empire.
1. Chapter 1

_(Note: This is a sequel to, and contains spoilers for, 'Mirror Universe Turnabout' and 'Infiltration')_

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Running on the treadmill to the left of mine in the gym this morning is James T. Kirk, captain of the starship Enterprise. I try not to stare, but I still find myself casting frequent glances sideways. He has no idea the person running alongside him is also James T. Kirk, and also once captain of the starship Enterprise. Just not the same Enterprise or the same James T. Kirk. But then why would he suspect anything? At the moment not only don't I look like him, but I'm not even a man. The name I currently go by is Jenna Lawson, and I'm the new Security Chief on the USS Enterprise.

In my own universe, a woman named Janice Lester swapped our bodies and fitted me with an undetectable 'bio-collar' that prevents me from telling anyone who I really am. Janice is dead now, killed by my science officer Mr Spock when he decided to take command of our Enterprise. Unfortunately, she was still in my body when she was vaporised, so I've travelled to this universe to steal the body of their Jim Kirk. Now that I'm here all I need to do is figure out how.

"Good morning, Captain, Jenna," said a female voice.

I turned to see Nurse Chapel get on the treadmill to the right of me, acknowledging her greeting with a smile and a nod.

Christine is one of those people who most surprised me by how different she was from her counterpart. This Christine Chapel is much more to my taste. If I thought she had any sexual interest in women I'd seduce her, but where my Nurse Chapel is happy to go with anyone, male or female, who shares her interest in pain, this one appears to be wholly heterosexual. Unfortunately. In fact it's obvious to everyone that she has the hots for Spock - obvious to everyone but him, that is. I'd first encountered her the day after coming aboard, when I reported to sickbay for my medical as part of my induction...

"Good afternoon, Lieutenant Commander, and welcome to the Enterprise," Dr McCoy had said, greeting me with a smile I wasn't expecting because, though a brilliant doctor, my McCoy was a cold, emotionally distant man more comfortable cutting up cadavers than dealing with the living.

"Nurse Chapel will get the basics off you and then I'll give you a thorough examination."

"Hello, Jenna, it's nice to see another woman joining us in a senior position."

That was my first sight of her, and I was enchanted. She might be physically identical to the Christine Chapel I knew, but she was a lot more wholesome and, well, _yummy_.

She recorded my height, weight, blood pressure, etc., then McCoy did the in-depth stuff.

"Hmmm," he said when his scans were complete, "I see you've had cosmetic surgery. Repair work?"

"Elective," I replied. "I didn't like my face so I had it changed. Chalk it up to female vanity. The procedure is fully covered in my Starfleet medical file, complete with before and after pictures."

This was a lie. I'd had to change my appearance because there was already a Janice Lester over here, counterpart of the woman whose body I'm stuck with, and she's known to Jim Kirk. Needless to say, the 'before' image in my file does not show Janice Lester but was selected from those turned up by an image search for faces that could plausibly have been mine before the surgery. It was as fake as everything else in my Starfleet records.

"Nothing wrong with a little vanity," McCoy had chuckled. "I once thought of doing something about the bags under my eyes, then decided I looked more authoritative with them. While you're in here is there anything we can do for you? I notice you haven't taken any contraceptive measures."

"No need," I said, "since I'm not sexually interested in men."

I'd given Christine a significant look then, and she had blushed, but we had still become reasonably friendly in the two weeks since, often sharing our mealbreaks with Uhura. Which was a whole other level of strangeness. I knew every inch of Uhura's body, having shared a bed with her counterpart for several weeks when I was her concubine.

Jim Kirk finished his session on the treadmill, grabbed his towel, and stepped off it.

"Ladies," he said, acknowledging us with a nod as he draped his towel around his neck and made for the exit.

I left myself a few minutes later, and headed out of the gym, towelling myself off as I walked to the turbolift. I would shower when I got back to my quarters.

Arriving at my deck, I emerged from the turbolift and was making my way along the corridor when someone rushed out from a side corridor, almost colliding with me. It was Kevin Riley.

"Sorry, sorry," he said, "my fault."

He scurried away, casting a wary look my way as he did so. I grinned. I had 'accidentally' broken Riley's arm during a friendly martial arts contest two days earlier. His counterpart had tried to rape me in our universe and it felt good to get some payback, even though I knew it wasn't really the same man. The fact that I was able to break his arm at all was also very satisfying. I'm smaller than I was, a woman, and with a lot less upper body strength than I had as a man. I've been training hard since this became my body, working to improve my strength and stamina, and all that effort was finally starting to pay off.

After showering in my quarters, I donned a bathrobe and sat down in front my mirror to do my hair and make up. I might be a woman now, but inside I'm still a man so this wasn't something I enjoyed doing. Since a certain level of personal grooming was expected of me, it also wasn't something I could really avoid. This done, I turned on my computer terminal. I had spent most of the time I had to myself getting up to speed how the culture and history of these people differed from my own.

"Computer," I said, "tell me about Zefram Cochrane."

"Cochrane, Zefram," said its mechanical voice, "born March 12, 2030 in Billings, Montana to Charles and Janice Cochrane. In aftermath of World War III, constructed humanity's first warp-capable vessel, the Phoenix, in Bozeman, Montana, using a Titan II nuclear missile dating from 20th century. On April 5, 2063, made Earth's first warp flight. Phoenix warp signature was detected by Vulcan survey ship, T'Plana Hath, which then made peaceful first contact with humans, including Cochrane, at Phoenix launch site."

A picture of Cochrane shaking hands with the Vulcans appeared on the screen, with their Cochrane looking much older than his years, just as ours had. Perhaps that was the point at which our histories diverged. When the Vulcans landed on my Earth, expecting a peaceful first contact, Cochrane killed their leader with a concealed weapon. He and his people then seized the T'Plana Hath. From that bold act, from that captured technology, the Terran Empire was born. The computer continued:

"Cochrane made flight playing Steppenwolf's 'Magic Carpet Ride' during lift-off."

The computer then started playing this, and I smiled - I've always liked classical music. On the screen a photo appeared of Cochrane as a teenager, with his father. I'd seen it before. It was one of the few photos from his childhood to survive the war in either universe.

In the afternoon I was called into a meeting of senior personnel in the conference room. Present were the Captain, Spock, McCoy, Uhura, and Mr Scott.

"Thank you for coming," said Kirk, when we were all seated. "Many of you have been wondering where we've been heading since we set off from Earth two weeks ago and up until now I've not been at liberty to tell you, such is the secrecy surrounding this mission. Since we're almost at our destination I'm now allowed to let you know, though by this point some of you will have guessed given our heading. But first, a brief recap for Lt Cmdr Lawson. Last year, while in orbit around the planet Halka, the Enterprise experienced a transporter malfunction during an ion storm that resulted in Mr Scott, Dr McCoy, Lt Uhura and I switching places with our counterparts in a parallel universe."

I tried not to show my surprise. So this mission was about _us_?

"Where we have the Federation, a political alliance of worlds working together," Kirk continued, "they had the Empire, an alliance of worlds conquered by Earth and absorbed into the Terran Empire. Cruelty and brutality were part of everyday life on their Enterprise with advancement in rank being achieved by assassinating those above you. Their Captain Kirk, my counterpart, succeeded to command of the ISS Enterprise by assassinating its previous captain, Christopher Pike. His first action as Captain was the suppression of a Gorlan uprising through the destruction of the rebel home planet. His second involved the execution of five thousand colonists on Vega Nine. Here, such a man would be a mass-murdering monster, but there he's a loyal servant of the Empire."

So that's what they thought of me.

"How did you find out so much about him?" I asked.

"With everyone believing we were our counterparts, I was able to access their computer records. Eventually, obviously, we found our way back to our own universe."

"You said you were switched with your counterparts. So if you were over there, then they were over here. Did they pull off the same trick and successfully masquerade as you?"

"They did not," said Spock. "They were taken into custody almost immediately."

I knew this, of course, but not what had given us away.

"I don't understand," I said, "how were you able to identify them as imposters so quickly?"

"It is far easier for civilised men to behave like barbarians, than it is for barbarians to behave like civilised men," said Spock.

Oh barbarians, are we? As Security Chief I carried a phaser on my hip at all times, the only one at the table who did so. Looking at them in that moment, at all those smug, sanctimonious faces, I felt an almost overwhelming urge to vaporise the lot of them. But I didn't, because despite their self-regard I knew the Empire was superior to the Federation. I was the living proof. Which of us had a spy in a position of trust on the other's Enterprise, after all?

"Our encounter with the Empire worried Starfleet Command," said Kirk. "It was obviously aggressively expansionist, and they were rightly concerned that if the Empire should ever discover a way of crossing over to our universe in force, we would become their next target. It was decided that if there was a way to make that crossing then we needed to discover it first in order to be prepared in the event of any incursion by them into our universe."

My ears pricked up at this news. Could it be...?

"As part of the Enterprise's recent refit," Kirk continued, "the deflector dish was fitted with a prototype device which the scientists who developed it claim will open a portal between our universe and theirs. Most of you have been kept in the dark as to our destination on this, our first mission since the refit. Ladies and gentlemen, that destination is Halka. That's where first contact between us occurred and that's where the scientists believe we have the greatest chance of a successful trial."

I remembered the Halkans. When I returned to my own universe that first time I discovered my counterpart had suspended the destruction for opposing us that Empire protocols mandated. Spock had reported 'my' actions to Starfleet Command and been instructed to wait until planet dawn over the principal target to allow me to carry out our mission. In the event we didn't, his orders were to kill me and to proceed against the Halkans as the new captain of the Enterprise. Needless to say, my first action on my return was to order the Halkans destroyed. One more race gone extinct because they foolishly chose to defy the Empire. Still, having them gone made it easier to mine their dilithium since you don't need to pay even lip service to any environmental concerns on the part of the locals when there are no locals. Spock had tried to argue for a logical reason to spare the Halkans, but there were none. That he had done so was my first inkling that exposure to the other Kirk, the Kirk in this room with me now, might have caused cultural contamination.

"Have we let the Halkan Council know we're conducting this experiment while in orbit around their planet?" asked McCoy.

"Of course," said Kirk. "We wouldn't be doing it without their permission. The Federation is not the Empire."

That was true. Permission? From those weaker than yourself? Madness! I would never understand these people. The only true morality, the only one that mattered, was that might makes right.


	2. Chapter 2

Halka looked much the same in this universe as it did in mine. The Enterprise had arrived here and achieved orbital insertion two hours ago. We were currently moving into the same position relative to the planet and its star as last time. This was supposed to maximise our chances of forging a link between the two universes once more. That was the theory, at any rate. I wasn't convinced this was going to work, but there was no way I was going to miss it. Which is why I was on the bridge when the test commenced.

"We are ready to proceed, Captain," said Mr Spock, frowning over his instruments, "though I must caution you again that the power required for this exercise will leave the Enterprise without shields and phasers while the device is active."

"Duly noted, Mr Spock, but we're just going to have to chance it. Any sign of hostiles nearby, Mr Sulu?"

"Negative, Captain," replied the helmsman, "we appear to be the only vessel present for several light years in every direction."

"Then proceed, Mr Spock."

Spock depressed a button on his console and our deflector dish began emitting a high energy beam of exotic particles focussed on an area of space a kilometre or so in front of the Enterprise. We followed the action on the viewscreen as the beam shot forth, watching for something to happen.

And then it did.

A disk started to form, a circle of space outlined by a glowing rim. It grew rapidly until it was larger than the ship, forming a window into another universe. And on the other side of that window, facing us, was another starship projecting an identical beam from its own deflector dish. The disk had formed at the interface where the twin beams met. We recognized the other ship immediately.

It was the Enterprise.

I frowned. Had my Spock taken possession of a similar device in our universe and been ordered to Halka to test it? But no, this wasn't my Enterprise - the markings were wrong. Which meant it wasn't my universe on the other side of that portal, either.

"We're being hailed, Captain," said Uhura.

"Onscreen, Lieutenant."

An image appeared of the bridge of that other Enterprise, but it might just as well have been a mirror. There was no analog of me, but they were all there, Kirk, Spock, Uhura, Chekov, Sulu, all dressed in regulation Federation uniforms.

"Greetings, Captain," said the other Kirk, "and may I say that's a fine looking crew you have there."

"I believe I can say the same of your crew, Captain," chuckled our Kirk.

"This is an historic moment, the first contact between our two universes. I'd very much like to meet in person. May we send over a party."

"A private word, Captain?" said Spock.

"You'll have to excuse me, Captain," said our Kirk, "I'll get back to you shortly."

"Of course," other Kirk replied, as Sulu broke the connection.

"What is it, Mr Spock?"

"I tried scanning the other vessel but could not. They are blocking all scans. Additionally, while you were communicating with their captain, I analysed the image we were receiving from their bridge and believe it is being altered as it is transmitted."

"So they're hiding something?"

"That would appear to be the case, yes."

"Keptin," said Chekov, "the other ship has just beamed down a landing party to the capital city of our Halka."

The portal between our universes was large enough that each of us could see some of the other's Halka through it. That had been enough for them to beam a landing party through as the Halkan capital city came into view.

"Size of the landing party, Mr Chekov?"

"Twenty people, all apparently unarmed."

"Twenty? That means their transporter has more pads than ours."

"There's something else," said Chekov.

"What is it?"

"They're registering as human, but not entirely so."

"'Not entirely so'? What does that mean?"

"I'm sorry, Keptin, I don't know how else to describe it."

"Uhura, re-open communications."

"Aye, Captain."

The bridge of the other Enterprise appeared on the viewscreen once more, complete with its smiling crew. There was something unnerving about the way they all smiled at us, even their Spock. It seemed almost...predatory.

"Why have you beamed a landing party down to our Halka?" asked Kirk.

"We are explorers, Captain, our Prime Directive compels us to seek out new worlds, new civilisations, and to boldly go where no human has gone before."

"A fine sentiment, and one we share, but the diplomatic protocols of first contact require us to begin by establishing agreed procedures before this sort of incursion takes place."

"'Incursion'?" said other Kirk. "You make it sound like some sort of prelude to invasion. We beamed down twenty specialists, none of them armed, as I'm sure your scans will confirm. We would be perfectly happy for you to beam a similar team down to our Halka. Please feel free to do so."

"Thank you, but we'll hold off for now. Clearly, we have opposing approaches to first contact. These are the kinds of cultural differences that can lead to real problems if we don't explore them first and resolve any areas of possible conflict."

"I see your point and appreciate your concern. Perhaps we could meet on your ship to discuss these matters?"

They seemed awfully eager to get aboard our Enterprise. Too eager.

"Keptin," said Chekov, "twenty people just beamed up to their ship from the planet."

"So their landing party has returned?"

"No, these were not the same people."

"Why do you have Halkans beaming up to your ship?" our Kirk demanded of his counterpart. "Did they come of their own free will?"

"Of course, Captain, what do you take us for? The Halkan Council sent up a delegation to greet us."

That didn't sound like the Council, that didn't sound like them at all. The Captain agreed.

"So quickly?"

"We can be very persuasive."

"Keptin," said Chekov, interrupting. "Those strange readings I got from the twenty who beamed down..."

"Yes?"

"I'm now getting them from forty, no fifty..."

"What is going on?" said Kirk, leaping to his feet.

"Teams from the other ship have beamed into transporter bay and deflector control," said Sulu. "We've been boarded, Captain."

"Cut the beam from the deflector dish, _NOW!_"

Chekov's fingers raced over his console, to no avail.

"I..I can't, Keptin! We're locked out!"

I had redshirts stationed in deflector control. I took out my communicator and flipped it open.

"Radic? Michaels? Come in please."

Silence.

I tried the transporter room.

"This is transporter chief Williams," said a voice over the sound of phaser fire, "they're over-riding our lock-out and pouring through and...no!"

He screamed, and the line went dead.

"What are you doing?" demanded the Captain, shouting at his counterpart.

"I should have thought that was obvious. It's the interaction of the beams from our two deflector dishes that creates the portal and is keeping it open. We knew you'd turn yours off as soon as you realised we were a threat, collapsing the portal, and we couldn't have that. While we could beam down to the planet, something about the exotic particles we're both emitting to form the portal, some sort of interference, was preventing ship-to-ship transport. We kept you talking until we could figure out how to compensate for this, which we have."

"Captain, I believe I am now able to penetrate the false image they are projecting and display what lies beneath."

"No need, Mr Spock," said the other Kirk. "The time for subterfuge is over, so let me save you the effort."

The image changed. For the first time we saw the other bridge as it really was.

"Bozhe moi!" swore Chekov, while Uhura gasped, her hand flying to her mouth.

The rest of us were shocked into silence by the sight, and by the sudden realisation of just how much trouble we were in.


	3. Chapter 3

They were still the Enterprise bridge crew, still Kirk, Spock, Uhura, Chekov, and Sulu, but their skin was grey and deathly, their eyes bone-white orbs with small black dots where healthy pupils should be. But worse than this was what we could see of the floor of the bridge. It was littered with bones.

Human bones.

The door onto the bridge opened, and two redshirts emerged from the turbolift with a terrified Halkan male between them.

"You probably wondered why we were beaming Halkans aboard, Captain," said other Kirk. "The reason is simple: I have a crew to feed."

The redshirts threw the Halkan on the floor in front of him. Immediately, Kirk and the rest of the bridge crew fell on the man, sinking their teeth into his flesh in a feeding frenzy. His screams were cut short when Spock ripped out his throat in a spray of blood.

"Cut transmission," said our Kirk, finding his voice at last. "Mr Chekov, seal the transporter room doors and try to modulate the deflector beam. We may not be able to turn it off, but let's see if we can get it interfering with ship-to-ship transport again."

"Transporter room doors already sealed by our people before they were overwhelmed, Keptin," he replied. "Working on beam modulation now."

We were all stunned by what we'd just witnessed.

"What...what was that?" said Uhura, visibly shaken. "What _are_ they?"

"Zombies," said Sulu, "it's a ship full of zombies."

"Fascinating," said Spock, "in it's physical manifestation, their condition somewhat resembles that of Vulcans who have been exposed to large amounts of Trellium-D."

"I doubt it's Trellium-D," said Kirk, "and there's no such thing as zombies. Whatever those people may be they're not reanimated corpses. Mr Chekov, do another scan of the Halkan capital for not-quite human life signatures."

"Number now one hundred twenty, no two hundred..."

"They appear to be deliberately spreading their affliction," observed Spock. "It would be helpful if we knew the means of transmission."

"We're in no position to aid the Halkans until the ship is secure. We have to cut our deflector beam. Lawson..."

"On it, Captain," I said, heading for the turbolift. On the way down I called in all those redshirts currently off-duty. I needed everyone. By the time I reached the deck deflector control was on everyone knew what was required of them and were heading to their assigned posts. As the doors opened, I took off at a run, being joined by several redshirts on the way. When we got to deflector control I found Scotty and several of his engineering crew engaged in a gun battle with the...hell, let's call them zombies...who had occupied it and barricaded themselves in. Scotty was pleased to see us.

"You're a sight for sore eyes, lass," he said.

"What's the situation, Mr Scott?"

"We've got four hostiles behind the barricade keeping us out, while a fifth is getting up to who knows what deviltry inside. We've hit them several times with stun beams from our phasers but they have no effect. Unfortunately, the same is not true of us. They've stunned several of my men."

"Have you tried phasers on full power?"

"No, we most certainly have not. The walls and hull will dissipate even a full power beam from a hand phaser, but there's all manner of sensitive systems and devices protruding from those walls that a beam designed to vaporize would destroy. We could end up disabling the ship. And if we start firing off full power beams at them, they're liable to do the same to us."

"Oh, I doubt that," I said. "The last thing they'll do is try to vaporize you."

"And why would that be?"

"Because they want to eat you."

"What?! Are ye joking?"

"I wish I was. Hmmm. Despite their ablative properties, you can still cut through a wall with a focussed beam, right?"

"Aye, that I can - I once had to do so to get into main engineering and stop Riley from driving the crew mad with his singing - but I'm not sure what you're getting at."

"These may not be the zombies of legend," I said, adjusting the beam on my phaser, "but I'm betting they have the same vulnerability."

I took careful aim, and the next time one of the zombies poked his head out I burned a hole through it right between his eyes.

He went down and didn't get up.

"Okay lads," shouted Scotty, "adjust your phasers to cutting beam and let's get them!"

He was the first one to break cover and he led my men and his in storming the barricade. A few of ours were felled by stun beams, but they had the superior numbers. They soon overwhelmed the zombies, but not before one managed to bite one of my men.

"Are you okay, Wilson?" I shouted.

"Yes, ma'am, I'm...I...actually I feel a little strange."

I realized what was happening before anyone else.

"Quick, secure him," I ordered, "and be careful."

By the time they had tied him up, Wilson's skin was already turning grey, his pupils shrinking to tight little circles of darkness.

"Don't let him bite you!" I shouted, as someone realised the danger, tore a sleeve from the uniform of one of the downed zombies, and rammed it into Wilson's mouth.

Leaving them to deal with him, I went into deflector control, where Scotty had already put a hole through the brain of the zombie in there. He was examining the controls and shaking his head.

"Have you turned off the beam?" I asked.

"Och, if only I could," he said, "but I cannae. This wee devil has destroyed the overrides, encrypted the main controls, and somehow routed the power cut-offs through the ship's self destruct, which shouldn't be possible."

"What does that mean exactly?"

"It means that we can't cut off power to the deflector without immediately activating the self-destruct and destroying the Enterprise. If we try and move the dish from outside, same result. The only way to turn it off is by breaking the encryption on the main controls, and that could take days."

"We don't have days, Mr Scott."

"Aye, tell me something I don't know."

"Our ship can't use its shields or phasers while that beam is active so I'm guessing they can't use theirs either."

"That would be my guess as well, lass."

"What about photon torpedoes?"

"Aye, we could fire them, but the ships are so close that we'd destroy ourselves, too."

I left Scotty pondering his dilemma and rejoined my men.

"We let those outside the transporter room know to set their phasers to cutting beam," said one of them, Gupta. "The zombies are burning their way through the door, but now we'll be ready for them when they break out."

"Excellent!" I said. "I went everyone we can spare to get to the transporter room with a phaser. When the zombies do get through the door there need to be enough phasers on them to cut them to ribbons."

"What about Wilson?" asked Gupta.

Wilson was now wholly zombie, and struggling to break free of those holding him.

"Get him into a holding cell," I said, "but he remains tied up and the gag stays in. Also, get one of these corpses to Dr McCoy for autopsy and put the rest in cold storage until the Captain decides what he wants to do with them."

"Aye, aye, ma'am," said Gupta.

I headed back to the turbolift that had brought me from the bridge, trying to figure out what we could do about that beam from the deflector.


	4. Chapter 4

"The crew of the other Enterprise haven't launched an invasion," said McCoy as he worked, "they've launched an infection. They're a disease vector. Think of the portal as an open wound and their ship as a syringe full of infected cells they've injected into the body of our ship, sending forth diseased cells to corrupt the healthy cells - that would be the crew - of our Enterprise. Judging by the speed with which the infection has spread on Halka, its sheer virulence, if you had allowed even one of them to break through into the general population of the ship, we could have lost the Enterprise."

"That bad?" said Kirk, rubbing his chin.

"That bad, Jim," said McCoy. "If the situation had reached that point you'd have had no choice but to destroy the Enterprise, hopefully taking the other one with it. Whatever happens, we daren't let this thing gain a foothold in our universe."

"Do we know anything about the cause of the infection?"

The Captain, Spock and I were watching Dr McCoy dissecting the zombie with Nurse Chapel assisting him. We needed answers, and we needed them fast.

"Toxoplasma gondii!" said Dr McCoy, looking up from the corpse he was autopsying and snapping his fingers, the desired effect of this action thwarted by the rubber gloves he was wearing.

"Is that the disease causing this?" asked Kirk.

"What? Of course not!" said McCoy, looking at us as if we were idiots.

"Then why mention it?" said Kirk, sounding exasperated.

"I believe I understand what has the Doctor excited," said Spock. "The parasite Toxoplasma gondii is a protozoa that used to live in most warm-blooded animals on Earth and was heavily implicated in schizophrenia in humans. It prefered home was cats, where it reproduced. To return to its feline host, it manipulated the behavior of mice and other animals it infected, making them lose their fear of cats, who then ate them. This returned the parasite to a cat's body and so ensured the completion of its lifecycle."

"You think something similar is happening here?"

"It makes sense," said McCoy. "For organisms that lack any intelligence, parasites can sometimes exert remarkable influence on the behaviour of their hosts. The crew of that other Enterprise are all still as intelligent as ever they were, but that intelligence is being bent to a single purpose: spreading the infection."

"So the grey skin, the weird eyes, and the resistance to phaser stuns..." I said.

"All just the effect the parasite has on the host body. I'd theorize that the resistance to phaser stuns is due to some sort of super-charging of the nervous system, enabling it to withstand blasts that would paralyse someone not infected. I'll know more when I've studied the samples I'm taking from all this man's major organs."

"Will you be able to come up with a cure, something we can weaponize to use against the zombies?"

I smiled at this. Without noticing he was doing so, Kirk had also started calling them zombies.

"I doubt it. In the case of Toxoplasma gondii, once the parasite became deeply ensconced in brain cells, getting it out of the body proved impossible. It formed thick-walled cysts around itself that were impregnable to antibiotics. This thing, whatever it is, looks like Toxoplasma gondii on steroids and probably has defences to match."

"Well, keep at it, Bones. In the meantime, we need to get back to the bridge."

"When the other Captain Kirk lifted their image manipulation he also stopped blocking our scans," said Spock. "I suspect he did this for the psychological effect that seeing the charnel house his ship really is would have on humans. His doing so enabled me to download files from his ship's computers. With your permission, Captain, I would like to devote myself to the study of those files. If we are fortunate, they may contain something that will aid us."

"Good idea, Spock. Report to me with any findings."

Spock departed for his quarters, which left me and Kirk riding the turbolift up to the bridge together.

"I think I may have a way of disrupting their beam," I said. "What if we use a shuttlecraft?"

"If a shuttlecraft got in the path of those beams it would be destroyed," he said.

"Which is why I'm not proposing getting it in the path of the beams. What I had in mind was using it to damage their deflector dish by ramming it."

"That could work," he replied, looking thoughtful. "Scotty should be able to tell us where to aim for to cause maximum damage. But it would be a one-way mission. As soon as their deflector is damaged and the beam disrupted the portal will collapse, leaving whoever pilots it trapped in that other universe."

"Not necessarily," I replied. "I have a plan..."


	5. Chapter 5

"Remote control, is it?" Scotty had said when we put my idea to him. "Aye, I can do that. It wouldn't work over longer distances because of transmission lag, but at this range that wouldn't be a problem."

Which is how I came to find myself standing between Uhura and Spock's stations on the bridge, the remote control console Scotty had cobbled together for me balanced on the rail. In the time we'd spent pulling our plan together the zombies had beamed landing parties down to several other Halkan cities and beamed up more groups of Halkans. Before too much longer, the planet would be beyond saving.

The control console was much like those they had back in the days of primitive computer games, only larger and with a built in tricorder screen giving me telemetry from the shuttlecraft and a live feed from its front-facing video camera. Not that I needed the latter at the moment since the same video camera was supplying the image currently filling the Enterprise's viewscreen.

"Steady as she goes, Ms Lawson," said Kirk encouragingly, his back to me of course.

I had guided the shuttlecraft out of the shuttle bay and down under the ship, hugging the hull. We needed to conceal what we were doing until the last possible moment to reduce the amount of time the zombies had to launch any kind of counter-measures. Eventually, the shuttlecraft had traversed the length of the Enterprise and was tucked away under our own deflector dish.

"Shuttlecraft in position," I announced.

"Mr Sulu, switch viewscreen to regular view," said Kirk.

Sulu did so.

"Ready when you are, Ms Lawson."

Palms sweating, I pushed forward my levers and watched on the viewscreen as the shuttlecraft shot from concealment, heading straight for their deflector dish. As it did so, another shuttlecraft appeared from under their deflector dish, heading for our shuttlecraft. It happened too swiftly for me to react. The two met head on at the interface, the collision resulting in an explosion that destroyed them both.

"Bozhe moi!" said Chekov as the shockwave from the explosion reached the Enterprise, rocking us slightly.

The image on the viewscreen was suddenly pushed to the left by another until it occupied only half of the screen. The new image came from the bridge of the other Enterprise. Zombie Kirk was holding a remote control console identical to my own.

"Really, Captain," he said, "we're the same person. Did you truly think you could come up with a way of disrupting the deflector beams without me coming up with the exact same method. There's no move you can make that I won't anticipate."

I hadn't considered that. Of course we were going to arrive at the same solutions.

"Even our chief engineers think the same way," said zombie Kirk, "that's why the remote control consoles we're holding are identical."

Wait, what?

Kirk stood up. In his hands he was holding a console identical to my own. So Scotty had made two. But why...?

"I'll bet you didn't anticipate this," he said, moving the control levers forward.

A second shuttlecraft shot out from under our Enterprise, heading directly for their deflector dish. It had to have left the shuttle bay directly behind mine to have already been in position. On their side of our viewscreen the zombies all got to their feet and stared at us, expressions blank. It was deeply unnerving.

The shuttlecraft slammed into the area of the deflector dish Scotty had told us to aim for, the front crumpling, before bouncing back from it and drifting lifelessly. At first, it looked as if we had accomplished nothing. Then their deflector beam started to flicker before melting away entirely, followed by the portal collapsing and their onscreen image winking out.

They were gone. We had broken free of the zombie Enterprise.

But our own beam was still on, shooting energy into space.

"We're still vulnerable as long we can't turn our deflector beam off," I said. "What if the zombies get their deflector repaired in time to hook us again?"

"They won't," replied Kirk. "I had Scotty pack the second shuttle with explosives and rig up a five second self-destruct. Just before the portal closed I sent the signal to start the timer. The explosion won't be large enough to destroy their Enterprise, but it will cripple them and wreck their deflector dish beyond hope of repair. They'll have to spend months in spacedock undergoing repairs before they're a threat to anyone again."

Now I was really impressed, but also puzzled. Zombie Kirk and I had had the same idea because we were versions of the same person, but that should also have been true of Captain Kirk. Yet he had come up with a back-up ploy that neither of us had foreseen.

How was that possible?


	6. Chapter 6

Working together, it took Spock and Scotty fourteen hours to break the encryption. Impressive, but for fourteen hours we were beaming energy into space, depleting our power reserves, and pretty much defenseless.

"I want to open by commending Mr Spock and Mr Scott for finally shutting off the beam from our deflector. Sterling work, gentleman."

In the conference room were Kirk, Spock, Scott, McCoy and myself.

"I guess we have to chalk this test up as a failure," I said.

"We did succeed in opening a portal to another universe," observed McCoy.

"Aye, just not the one we wanted," added Scotty.

"We should've expected that," I said. "There are an infinite number of parallel universes out there. What are the chances we'd find one particular universe?"

"The scientists who created the device believed the prior contact between our universe and that of the Empire at this location might have created a weak spot between the two that we could exploit," said Mr Spock, "evidently, that belief was erroneous."

"We cast our energy beam out there like we would a fishing line," I said, "and what we hooked was the zombiverse's own fishing line. Even after we'd cut them loose, our 'fishing line' was out there for another fourteen hours. We got lucky and didn't make another contact, but who knows what else we might have hooked? We could've opened up a portal to a universe even worse than the one we did. I'm sorry, but absent a means of knowing exactly where the portal you're opening leads to, the device strikes me as unbelievably dangerous and further use of it would be foolhardy in the extreme."

"I'd have to agree," said Scotty.

"Me, too," said McCoy.

"I'm minded to agree with you, but what if the Empire finds a way to cross over into our universe?"

"Based on your reports on what you saw of their technology, it seems unlikely they would be any more successful than we've been," I said.

"I concur," said Mr Spock.

Kirk looked around the table at each of us then nodded.

"Then that will be my recommendation to Starfleet. Right, what do we know about the zombies? Mr Spock, what did their files reveal?"

"The contagion encompasses most of that other Federation. Which has become in effect an organisation devoted to spreading it."

"How long ago did they become infected?"

"Five years."

"_Five years!_" said Scotty, sounding appalled. "It took over their Federation that fast?"

"So it would appear."

"I've never seen anything like it," said McCoy. "We have tissue exemplars on board from a dozen different races including Human, Andorian, Vulcan, even Klingon, and this thing rampaged through all of them. Usually the species barrier offers some protection, but this acts like it doesn't even exist."

"Och, we've encountered some strange and terrible things in our travels, but what hellhole of a planet could produce such an abomination? Do we know?"

"Oh yes," said McCoy, "it came from Earth."

I think I was as stunned as Kirk and Scotty were by that news.

"That can't be!" said Scotty, shaking his head.

"DNA doesn't lie," said McCoy.

"The parasite appears to be a bioweapon developed during Earth's third world war," added Spock, "but never deployed. It was only rediscovered five years ago on both Earths, in a buried facility, during excavations in northern France. The team leader, Dr Christiane Deschanel, recognized how dangerous the dormant cultures were and recommended they be destroyed immediately. Her superiors over-ruled her, and instructed her to secure them. On our Earth, she disobeyed, destroyed them, and was fired. On their Earth, she obeyed her orders. Subsequent careless handling in an orbital lab staffed by scientists from across the Federation led to the parasite infecting those working there and escaping into the galaxy."

"So that other Enterprise crew could've been us?" said Kirk.

"I can find no difference between their history and ours until five years ago and the discovery of the bioweapon."

"Then they _were_ us!"

It was a sobering realisation.

"Who in his right mind would ever create something like that?" said Scotty.

"World War III was a dark time in your world's history," said Spock.

"It certainly was," said McCoy, "and when I next get back to Earth I'm going be doing is looking up our Dr Deschanel and getting her a drink."

"Aye, an' I'll be getting her the next one," said Scotty.

"Given the danger they represent," I said, "I'd like permission to vaporize the zombie corpses and their effects."

"Permission granted," said Kirk. "Dr McCoy has his tissue samples and we have a living zombie in Crewman Wilson so we don't need them."

"Aren't we taking a risk keeping him around?" I said.

"'Keeping him around'?" said McCoy, giving me a look like thunder. "Good God, woman! Wilson is a member of this crew, one currently afflicted with an illness, and he should be treated as such."

"But it's not as simple as treating him just like any other patient, is it? Does he have any immediate prospect of recovery?"

"Not immediate, no."

"Then in the meantime, how are you going to feed him?"

"I don't..."

"He eats _flesh_, Doctor," I said, cutting him off, "living human flesh. Do we find him some, or do we starve him?"

"Let's table that discussion for now," said Kirk, "and get back to Halka. How do we contain and push back the outbreak down there?"

"I've been studying the tape of the zombie bridge crew eating that Halkan," said McCoy, "and a question occurred to me: why don't they eat each other? Their captain said he was abducting Halkans because he had a crew to feed, so clearly they need fresh meat. It was seeing the speed with which they ate, the frenzy of it that gave me my answer. They don't each other because they won't or can't eat the infected. Given how quickly a bite will infect and 'turn' a victim they have to eat him as quickly as they can before he becomes inedible to them."

"Very interesting, if you're right," said Kirk, "but what are the implications for Halka?"

"Well, if you infect everyone you leave yourself with nothing to eat, so my guess is when the infection reaches a certain point it levels off and the zombies don't deliberately create any more of their kind. From then on everyone else is food. Of course, what that means is..."

McCoy was interrupted by Uhura appearing on the screens on the three faces of the conference table computer terminal with an impeccably timed announcement.

"We've received a message from the leader of the Halkan Council," she said, "he wants to speak to the captain."

"Put him on, Lieutenant," said Kirk.

The face of Tharn, leader of the Halkan Council, appeared on the screens. Despite myself, I gasped. I recognized him, but he was not the same man. His skin was grey and deathly, his eyes bone-white orbs, his pupils shrunk to small black dots.

"Ah, Captain Kirk," he said, "I'm speaking to you on behalf of the council to tell you that you are now forbidden to send down landing parties and we require you to depart from our planet's orbit immediately."

"I don't believe that's you speaking," said Kirk, "not really. You're under the influence of an alien parasite."

"I don't care what you believe," said Tharn. "I am the duly elected spokesman for my people, leader of the governing authority, and under the rules of your own Federation, you are required to defer to my wishes in these matters."

"Technically, that's true," said Kirk, "but I'm also charged with acting in the best interests of the galaxy, interests that won't be served if I do what you ask. For now, we will respect your authority when it comes to the surface of your planet and won't attempt to send people down, but know this: we will also not allow anyone to leave your planet. You may only have sub-light craft and the ability to travel no further than your own star system, but any ship attempting to leave your world will be destroyed. As of now Halka is under quarantine, and that quarantine _will_ be enforced - with firepower if necessary. Kirk out."

With that he cut the transmission. On the one hand, I was impressed by his firmness in regard to imposing a quarantine that would be backed up by force, but on the other I couldn't believe he wasn't already firing on their cities. Halka was now beyond saving and harbored an infection that threatened the galaxy. The only sensible thing to do with such an infection was to burn it out.

"As I was saying..." said McCoy, "when the infection reaches a certain point it levels off and the zombies don't deliberately create any more of their kind. From then on everyone else is food. Of course, what this means - and as we've just seen - is they're most likely to want to 'turn' those in positions of power since that will make it easier to control a population that has essentially then become a food herd."

"The designated authority on the planet has forbidden us from doing anything more," said Kirk. He looked tired. "When Starfleet diplomats get here they will have to make the determination as to whether or not the affliction the ruling council is suffering from permits us to override their wishes. That aside, when more ships arrive we'll have to destroy the Halkan's space travel capabilities, of course."

"Naturally," said Mr Spock. "It is logical to assume the teams beamed down from the other Enterprise included engineers with the knowledge required to make Halkan space craft warp-capable. That cannot be permitted to occur."

"I'm sure we can confine the infection to this world," said Kirk, "but let's face it: we lost Halka. This is a dark day for the Federation."


	7. Chapter 7

"Zombies," said Admiral Cartwright. We weren't in the same room or even the same sector of space, but I could imagine him shaking his head.

"To all intents and purposes, yes," I said, sinking my fingers into a tub of cold cream, "but then if you go trying to break through to another universe without knowing its address you have no way of knowing what you're going to get."

Wearing only a nightdress, I was sitting in front of the mirror in my quarters and working cold cream into my face to remove my make-up prior to retiring for the night. It was also my first opportunity to report in to Larry Cartwright, the Empire's other spy in the Federation. This was one of those quiet periods when the crew were allowed personal conversations with family back home, and our covert communication was riding the carrier beam between the Enterprise and Earth, lost in all the chatter.

"Nevertheless, their device created a portal to another universe big enough for a starship to pass through. We haven't managed that yet. Our trans-dimensional harnesses only allow for travel by individuals."

"Yes, but at least we can find the universe we want to. The Federation doesn't know that deep in the sub-atomic structure of every piece of matter from a given universe is a vibrational signature unique to that universe. This is its 'frequency', and thus its address. Not having any matter from another universe, they had nothing to compare to their own and therefore no way of even realising such a thing even existed. We had the USS Defiant, a whole starship from their universe of the present day, that fell through a spatial anomaly into ours a hundred years ago. We've known about those vibrational signatures for decades."

A century of studying the Defiant's computers and technology had given us a lot of advantages over the Federation. We had long since cracked all their current encryption and codes, for example, and had sub-dermal communicators that they could not detect and which would enable us to communicate with each other without starfleet knowing about it. This was how I was reporting to Larry Cartwright now.

"The incursion from the zombiverse could have given them a lot of material to work with," said Larry, "they could discover vibrational signatures exist that way."

"Already thought of that," I said, using a wetwipe to remove my lipstick, "when Captain Kirk gave me permission to vaporise the zombie corpses and all their effects, I made sure those effects included their phasers and every bit of equipment of theirs we had captured. Debris from the shuttlecraft they crashed into ours at the portal interface drifted back over to their side before it collapsed. That left only Crewman Wilson who, tragically, had to be vaporized when he broke free of his guards while being transferred from his holding cell this afternoon. His bonds had somehow been loosened before then. I can't imagine how."

"Good work," chuckled Larry. "So you got everything?"

"Yes, apart from the tissue samples Dr McCoy took. I'm confident those will only be looked at medically and aren't likely to have their sub-atomic structure investigated the way, say, a surviving phaser might. No, other than those samples, only a strip of material I tore from the sleeve of one of the zombie corpses survives beyond the surface of Halka. I'll get it to you via our dead drop next time I'm on Earth and you can make sure it gets back to the Empire. I'm sure our scientists would be interested in having the vibrational signature of another known universe."

"I'll be sending it across with the schematics of the device they used to open the portal. The Federation may not know how to find a particular universe but we do. They don't know it yet, but they've just given us the means to invade them."

"Good. How is the infiltration proceeding?"

"We've brought six more of our people over, all cadets, to replace their counterparts in Starfleet Academy."

"Why cadets?"

"I may have replaced their Admiral Cartwright, but the Council believe that attempting to replace more high ranking people is too risky at this point. Better to get cadets in place and have them move up the ranks. By the time we're ready to invade, years from now, many of them should be starship captains. We're going to hollow out the Federation from the inside. Oh, and I have a bit of news that may interest you. Starfleet Command has decided to do away with the post of Security Chief and combine it with that of Chief Tactical Officer."

"It's no skin off my nose," I said, shrugging. "I should be done here by the time the change comes into effect. Before I sign off, did you get me the information I asked for?"

"I did," said Larry, "and it surprised me. Why did you want me to look up Federation records on Camus II?"

"Because my last mission undercover took me to our Camus II and I discovered a cache of extremely dangerous bioweapons there, which our James Kirk had to destroy," I lied. "As this affair with the zombies has shown, you can't be too careful with such things."

"Yes, well, the file was marked 'top secret' and no one of lower rank than admiral was going to get into it."

"What did it say?"

"It appears that your counterpart, the Janice Lester of this universe, discovered a mind-switching device on Camus II and used it to steal the body of their Captain Kirk. Their minds were eventually returned to the correct bodies, but not before she was able to briefly take command of the Enterprise. You can see why Starfleet is keeping the existence of the device secret, of course?"

"Just the knowledge of its existence could be politically and socially destabilising."

"Exactly. We'll have to decide what, if anything, we're going to do about it."

After Larry broke the connection, I wiped the cold cream off my face and stared at my reflection, studying the face of the woman gazing back at me. Could it be? Janice Lester had swapped bodies with us in both universes. In this one, officially, Kirk had got his body back. But what if he hadn't?

What if the man sitting in the Captain's chair on this ship right now was actually Janice Lester?

It would explain a lot of things, and give me much to think about. I smiled. Oh yes, so much to think about...

"""""""""""""""""""

The End

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_Incidentally, Toxoplasma gondii is a real thing. If you're interested, check out an article called 'How Your Cat is Making You Crazy' at The Atlantic from a few years ago. Spooky stuff._


End file.
